Cellulose compositions combined with fire retardant materials are widely used in the construction industry. Specifically, fire-resistant cellulose materials are traditionally used for thermal insulation in the walls and attic spaces of homes and commercial buildings. Insulation products of this type are designed to prevent heat loss and correspondingly insulate building structures from the outside environment. Raw materials used to produce cellulose insulation products may involve many different paper compositions ranging from recycled newspaper to cardboard, paperboard, and fiberboard. These materials are physically processed to produce a finely-divided material having a low bulk density.
To achieve an approved level of flame and smolder resistance, the selected cellulose materials are combined with fire retardant compositions during the production process. Many different fire retardants may be used for this purpose, which are traditionally applied in powder form. Exemplary fire retardant compositions include but are not limited to monoammonium phosphate, diammonium phosphate, boric acid, ammonium sulfate, sodium tetraborate and mixtures thereof. These materials, as well as other fire retardant compositions and additional information regarding the production of cellulose insulation products are discussed in U.S. Pat. No. 4,168,175 to Shutt and U.S. Pat. No. 4,595,414 to Shutt, the disclosures of which are incorporated herein by reference.
After combining the selected fire retardant compositions and cellulose materials, the resulting product is physically processed using conventional mechanical devices (e.g. hammermill systems known in the art) to produce a pulverized, finely divided insulation product. In accordance with traditional processing technology, fire-resistant cellulose insulation products are specifically prepared using one of two basic methods. In a first method, the selected cellulose materials (e.g. recycled/used paper products) are subjected to multi-stage size reduction by grinding or other conventional processes using standard equipment including but not limited to hammermill systems. At selected stages during the size reduction process, a fire retardant composition in powder (dry) form is combined/mixed with the cellulose materials. In a preferred embodiment, mixing of these ingredients is undertaken at or near the final grinding/shredding stages of the system.
Alternative “hybrid-type” systems have been developed which involve addition of fire retardant compositions in powder (dry) form at or near the final size-reduction stages of the system in combination with the use of a liquid fire retardant composition in the initial stages of production. However, both of these systems require the use of powdered (dry) fire retardant compositions which present numerous disadvantages. These disadvantages include but are not limited to (1) the generation of substantial amounts of dust which requires elaborate safety and environmental control systems; (2) the need to use large amounts of chemicals (e.g. fire retardants) due to production inefficiencies associated with powder-type systems; and (3) increased material costs associated with the need to use large quantities of powdered chemicals.